The use of an implantable infusion port for the delivery of drugs is well known in the art. Current devices typically comprise a needle-impenetrable cylindrical reservoir connected to a catheter for placement into an appropriate vessel that is accessible from the exterior through a generally planar septum that covers the reservoir. The purpose of an implantable infusion port is to provide the user with means for frequent blood sampling, delivery of medications, nutrients, and blood products, and imaging solutions to the patient's blood stream or desired location within the patient's body. The implantable infusion port is accessed by use of a special needle that may be inserted through the patient's skin and through the penetrable septum to access the reservoir. Current devices generally possess a cylindrical reservoir to be accessed by the user. A standard port contains a reservoir with straight walls and generally flat bottom base and an outlet catheter at the junction of the reservoir and base. The use of a cylindrical reservoir with straight walls and a flat bottom, however, creates “corners” or angular junctions, specifically where the bottom wall of the reservoir meets the continuous side wall. The design of a cylindrical reservoir will necessarily require the side wall of the reservoir to meet the bottom wall at approximately a ninety degree angle. One example of a cylindrical reservoir in an implantable infusion port is disclosed in U.S. Pat. No. 4,673,394. Although cylindrically shaped reservoirs are commonly used in such implantable devices, the angular junctions in such reservoirs may pose significant health risks to the patient over time. As will be discussed further below, a major issue with implantable infusion ports is the accumulation of debris and residue over time that may eventually lead to an infection for the patient and the occlusion of the device. With current port technology, such angular junctions are present not only where the bottom wall of the reservoir meets the continuous side wall, but also where the continuous side wall meets the planar septum covering the reservoir. The use of a generally planar septum to cover the cylindrical reservoir creates an additional angular junction where the side wall of reservoir meets the planar septum. The current technology therefore teaches a 90 degree angled junction at both the perimeter of the bottom wall and the top edge of the side wall where the side wall meets the bottom surface of the septum, thereby creating a large area in which debris and residue can accumulate and cause complications for the user. A significant drawback of the current technology is that the design of the reservoir and septum provides ample opportunity for debris and residue to accumulate which may compromise the safety of the patient over time.
Although the prior art, such as U.S. Pat. No. 5,713,859, may suggest a reservoir base with a slight radius or chamfer at the bottom of the reservoir to reduce the potential for debris build-up, such a design does not solve the problem of debris build up. A chamfered or rounded base still poses an angular junction where the continuous side wall meets the planar septum covering the reservoir.
Once implanted, infusion ports may remain in the body for periods of months to years. Due to such lengthy periods, the reservoir of the port can become contaminated and begin to harbor agents of disease. This can lead to problems, such as infection within the fleshy pocket beneath the skin occupied by the infusion port and blood borne infection traveling throughout the body. Such infection can require extensive therapy which may include removal of the infusion port. Currently, there is no practical way to monitor the effectiveness of the cleansing practice while the infusion port is implanted in the body and hidden under the skin.
As a result of investigating the fate of various discarded infusion ports recovered after being implanted and employed in the manner described above for various periods of time, it has been discovered that in almost every case the reservoir contained a deposit of clotted blood and/or drug residue. When allowed to stagnate, blood will form a cohesive mass, or coagulate, which is the body's natural mechanism to protect itself against excessive bleeding from a wound. According to principles of fluid dynamics, stagnation occurs in corners or areas where turbulence occurs. This issue with current ports, therefore, is that the presence of angular junctions and corners in the port reservoir can allow the blood to stagnate, and, once the blood coagulates, it can become very difficult to flush out. Sophisticated lysing drugs would then become necessary to dissolve such residue.
In many cases the residue, when cultured, exhibits the presence of bacterial and fungal organisms, such as Staphylococcus aureus, Staphylococcus epidermidis, and fungus of the genus Candida. In an attempt to clear the debris which can accumulate, especially at the angular junctions within the reservoir, thrombolytic agents have been developed. The use of such sophisticated materials to remedy an inherent infusion port design problem is expensive and puts the patient at risk of both infection and adverse reactions from the lysing agent.
What is required, therefore, is an implantable vascular access port that overcomes the drawbacks of the current technology by having a novel reservoir and septum design that attempts to eliminate angular junctions and improve flow patterns within the reservoir.
In addition to eliminating these angular junctions and improving flow patterns, another aim is to reduce the reservoir volume, or “dead space”. Due to a cylindrically shaped reservoir, current port devices possess a necessarily larger reservoir, and, therefore, a larger “dead space.” The distance between the bottom surface of a septum and the bottom of a reservoir base is a fixed number. This volume of the cylinder is termed the “dead space.” It is believed that the larger the dead space, the greater the potential for residue and debris to accumulate. It is desirable, therefore, to have an implantable vascular access port causing minimal dead space while still maximizing the needle penetrable surface area of the septum.
Another drawback of current port devices is that the common method among practitioners is to introduce the needle perpendicular to the top surface of the septum. The rational for such method is that when introducing the needle into the septum, the entire tip of the needle needs to not only penetrate the septum but needs to pass below the bottom surface of the septum in order for the fluid being inserted or infused to flow freely from the tip of the needle. With current port devices having a planar septum, the point of the needle will in most instances be introduced perpendicularly to the planar surface of the septum, and, after the needle tip has been introduced, the needle tip will come into contact perpendicularly with the planar surface of the bottom of the reservoir as well. Therefore, in current devices having a planar septum, the plane of the septum and the plane of the bottom surface of the reservoir must be parallel. The obstacle with such a design is that at some points in the needle accessible area of the septum, such as the periphery of the septum, the needle tip may not have clearance through the bottom of the septum and therefore not able to freely infuse or introduce fluids. What is desired, then, is an implantable vascular access port wherein the user is capable of introducing a needle perpendicular to the surface of a septum but wherein the plane of the septum is not necessarily parallel to the bottom of the reservoir.
Current vascular ports are also designed to have an outlet opening connected to an outlet tube, such as a catheter, to allow the flow of fluids from the reservoir to such an outlet tube. The issue present with current vascular access ports is that the outlet opening in the reservoir does not aid in the flow pattern of the fluid flowing from the reservoir to the outlet tube. This is because the outlet opening and surrounding structure are ninety degrees relative to the side wall of the reservoir. Such geometry of the opening disrupts flow into the outlet tube. The present invention is directed at overcoming the drawbacks of the current technology by having a novel outlet opening design to aid in the flow from the reservoir to the outlet tube.